Identification of brain structures and networks encoding pain, hyperalgesia, pain control and sympathetic function acutely after stroke. A voxel-based lesion-behavior – network mapping study of acute stroke patients

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The encoding of pain, hyperalgesia and pain control mechanisms in the brain is incompletely understood. The same applies for encoding of sympathetic nervous system function. The specificity of results of functional MRI (fMRI) studies, which investigated brain activation after repetitive short pain stimuli in healthy subjects, was recently challenged because of the non-physiological salience of the short-lasting pain stimuli. This project will overcome this shortcoming by investigating sensory (including pain perception, hyperalgesia, pain control assessed by quantitative psychophysics) and sympathetic dysfunction as a clinical phenotype 2-7 days after stroke before central reorganization processes take place. The behavior will be correlated to brain lesions in structural MRIs of ~200 patients by voxel-based lesion-behavior mapping (VLBM). Since the originally described VLBM might be not sufficient to detect single brain lesions, which alone are responsible for complex sensory behavior (e.g. hyperalgesia or pain control), the analysis will be extended to “behavioral–brain network” mapping. This will be achieved by making use of datasets of matched normal subjects mainly from the AgeGain project (Mainz data), which provides functional connectivity data and will allow us to assess the impact of individual focal brain lesions as seeds on brain networks. The connectivity data from individuals will be overlapped in a second step. We expect a higher overlap of the affected networks associated with a distinct phenotype than of the focal brain lesions themselves. Another approach will be to assess the impact of focal brain lesions on predefined resting state functional MRI connectivity (rs-fMRI) networks. The rs-fMRI scans will be obtained together with the structural scans. At the end of this project we will describe the brain networks that are responsible for encoding of pain, hyperalgesia, pain control and vegetative behavior. Moreover, the results of this study might become the basis for an envisaged longitudinal study uncovering the patterns of brain network lesions which can lead to chronic post-stroke pain months after stroke due to maladaptive brain reorganization.